The greatest obstruction to beautiful aquatic plants is algae growth. It is also the number-one cause of stress among aquarists. There are many species that are difficult to eradicate. Some of the most common are brown algae, hair algae (keijoo-sou), beard algae higejou-sou), norijou-soo, and aomidori. The causes of algae outbreaks are numerous, so it is difficult to speculate its occurance.
The brown algae appears when the aquarium is relatively new, its brown in color, and covers everything from walls to driftwood to leaves like a thin curtain. It is easily dealt with by adding a natural enemy, the best of which is Otocinclus. Plecos also eat it, but they may damage the leaves as well. The algae eater (Gyrinocheilus aymonierl) and the Siamese flying fox (Crossocheilus siamensis) also eat brown algae, but grow too large for a small tank or crowd the layout. The hair algae appears as long, thin hairs attached to driftwood, rocks, filter tubes, and old leaves. It may be green, gray or black, but is usually green in well-lit places. Outbreaks can be caused by infrequent water changes (high nitrate level) or too strong lighting (CO2 deficiency). This nuisance can be prevented by keeping the Yamato numa-ebi shrimp and bee shrimp in the aquarium from the start. (Left : Caridina japonica)
Beard algae is longer and thicker than string algae, but grows as a result of the same imbalances. It appears in relatively older tanks, growing on hard leaves like that of Anubias and Kurinam. Yamato numa-ebi won't eat it once it grows to a large size, so the shrimp should be kept in the tank from the beginning as a preventive measure. It doesn't grow profusely, but it is very unattractive. When changing water, it can be scraped off with your fingernails or sucked up with a vacuum. The red scat will clean an infested tank, but certain preparations need to be made for it. The pH level should be pushed up to around 7.5 or higher by stopping CO2 doses and, if necessary, adding potassium carbonate. Of course, the specimen must be one that has been acclimated to fresh water.
Nori jou algae is a bright green, mold-like algae that grows on the bottom sand and leaves. It produces a strong, moldy odor. It will break out in tanks with new filters and alkaline water, or as a result of too much light. Vacuuming is only a temporary measure because it grows back very quickly. A good quality filter is the best measure, and special herbicides or malachite green can also wipe out nori. (Right : Otocinclus sp.)
Aomidoro usually grows around the surfaces of plants, entangling in the dense growth of Riccia or willow moss, when this happens, it may be quite difficult to remove them. This type of algae thrives under the same conditions as aquarium plants, so it is not easily taken care of with water change method. Freshwater shrimps like the Otamajackshi and fishes such as black mollies, dwarf cichlids feed on it so it is relatively easy to deal with.
Many other types algae also exist, and most outbreaks are result of excess nitrates from too many fishes and infrequent water changes, dirty filters, or CO2/light imbalances. They can be largely prevented by cultivating the following good habits.